1. Field of the Invention
The present invention relates to a motor-operated stapler for bending leg portions of a staple in a well-shaped state along a bundle of sheets to be stapled irrespective of the thickness of the bundle of sheets.
2. Description of the Prior Art
Heretofore there has been known a stack tray of a copying machine which tray is provided with a motor-operated stapler. In this motor-operated stapler, a large number of rectilinear wires are arranged in parallel to form sheet-like staples, then a large number of such sheet-like staples are stacked within a cartridge and are sent out one by one from a delivery port formed in the cartridge. The cartridge can be accommodated with a magazine which is provided with staple forming/drive-out means.
Below the magazine is disposed a clincher base having a flat paper carrying surface for carrying a copying paper bundle thereon. The clincher base is slidably vertically with respect to the magazine so that the copying paper carrying surface thereof can approach or leave the magazine, thereby permitting a copying paper bundle to be pinched between the magazine and the copying paper carrying surface.
A slot is formed in the copying paper carrying surface for insertion therein of leg portions of a U-shaped staple, and a pair of clinchers are disposed pivotably within the slot to bend leg portions of the staple inwards along the copying paper bundle.
The clincher base is provided with a pair of clincher links for moving the paired clinchers pivotally, the clinchers being engaged respectively with one ends of the paired clincher links.
On a magazine housing side, to which the magazine is fixed, there are provided a pair of cams for moving the paired clincher links pivotally, with opposite ends of the clincher links being engaged with the cams respectively.
The cam for moving the clincher links pivotally is rotated by means of a motor which serves as a drive source for driving the magazine and a gear mechanism.
If the paired cams are rotated when the copying paper bundle is pinched between the magazine and a clincher table of the clincher base, the opposite end portions of the paired clincher links move pivotally following the rotation of the paired cams, while one end portions of the clincher links respectively cause the clinchers to turn, thereby bending the leg portions of the staple along the copying paper bundle.
In such a conventional motor-operated stapler, however, the clincher base is held vertically movably by the housing which holds the magazine and the clincher links, which are secured with shafts to the clincher base, move pivotally after a bundle of sheets to be stapled has been held between the magazine and the clincher base, so that the amount of the pivotal movement of clincher links differ depending on the thickness of the bundle of sheets to be stapled.
Therefore, if a copying paper bundle to be stapled is thick, the length of the staple leg portions projecting from the copying paper bundle is short and the distance from an abutment point between a fulcrum of each clincher link and each cam as a drive source becomes long, so that the amount of the pivotal movement of clincher links becomes small. Consequently, the amount of the pivotal movement for bending the staple leg portions projecting from the bundle of sheets to be stapled becomes small and there easily occurs a case where the leg portions cannot be bent sufficiently, with consequent occurrence of inconveniences such as the copying paper bundle being caught on projections or the like formed on a desk.
On the other hand, in the case of a thin copying paper bundle, the staple leg portions projecting from the underside of the bundle of sheets to be stapled is long and the distance from the abutment point of the clincher line fulcrum with the driving cam becomes short, so that the amount of the pivotal movement of clincher links becomes large. Consequently, the angle of the clinchers"" pivotal movement becomes large and there may occur a case where the bent leg portions of the staple again pierces through the copying paper bundle.
The present invention has been accomplished in view of the above-mentioned problems and it is an object of the invention to provide a motor-operated stapler of the type wherein a clincher base is held vertically movably on a magazine side and clincher links are pivotally moved by means of a drive source provided on the magazine side and leg portions of a staple are bent by clinchers, characterized in that the staple leg portions projecting from the underside of a bundle of sheets to be stapled can be bent at a predetermined certain angle irrespective of the thickness of the bundle of sheets to be stapled.
For achieving the above-mentioned object, according to the present invention there is provided, in the first aspect thereof, a motor-operated stapler wherein a bundle of sheets to be stapled is held by both a magazine which houses therein a staple forming mechanism and a plurality of staples and a clincher base which is movable in the thickness direction of the bundle of sheets and which is driven by a drive source provided on the magazine side, a staple is driven out from the magazine into the bundle of sheets, and leg portions of the staple projecting downward from the bundle of sheets are bent along the bundle of sheets by a pair of clinchers mounted on the clincher base, characterized by including clinchers"" pivotal movement control means which keep the amount of pivotal movement of the clinchers constant irrespective of the thickness of the bundle of sheets.
In the second aspect of the present invention there is provided, in combination with the above first aspect, a motor-operated stapler further including a clincher pivoting mechanism for moving the clinchers pivotally, the clincher pivoting mechanism comprising clincher links installed on the clincher base to move the clinchers vertically pivotally, driven cam surfaces formed respectively on the clincher links and extending in the thickness direction of the bundle of sheets to be stapled, fulcrums which convert swing motions of the cam surfaces into pivotal motions of the clinchers, and driving cams installed on fixing means side which hold the magazine, the driving cams coming into contact with the driven cam surfaces of the clincher links and being rotated by the drive source provided on the magazine side, and wherein the clinchers"" pivotal movement control means are formed respectively in upper areas of the driven cam surfaces with which the driving cams are in contact and are constituted respectively by projections for causing the clinchers to further turn in a direction to approach the surface of the bundle of sheets.
In the third aspect of the present invention there is provided, in combination with the above first aspect, a motor-operated stapler further including a clincher pivoting mechanism for moving the clinchers pivotally, the clincher pivoting mechanism comprising clincher links installed on the clincher base to move the clinchers vertically pivotally, driven cam surfaces formed respectively on the clincher links and extending in the thickness direction of the bundles of sheets to be stapled, fulcrums which convert swing motions of the cam surfaces into pivotal motions of the clinchers, and driving cams installed on fixing means side which hold the magazine, the driving cams coming into contact with the driven cam surfaces of the clincher links and being rotated by the drive source provided on the magazine side, and wherein the clinchers"" pivotal movement control means are constructed so that when the thickness of the bundle of sheets exceeds a predetermined value with respect to the length of staple leg portions, the distance between an abutment position and each of the fulcrums which abutment position is the position of abutment between each of the clincher links and each of the clinchers is increased relatively with respect to the distance between an abutment position and each of the fulcrums which abutment position is the position of abutment between each of the clincher links and each of the driving cams.